Electrically heated roll with electrical circuit



Jan. 19, 1965 w. H. NORTON 3,166,667

ELECTRICALLY HEATED ROLL WITH ELECTRICAL CIRCUIT Original Filed May 23.1960 INV EN TOR W////dm /7. Nari-an 3,166,56 atentd Jan. 19, 1965 UnitedStates Patent Oiiicc 3,166,667 ELECTRICALLY HEATED RGLL WITH ELECTRICALClRCUlT William H. Norton, Mundelein, Ill., assignor to ThermelIncorporated, Franklin Perl-r, Ill, a corporation of Delawere Originalapplication May 23, 1960, Ser. No. 39,971, now Patent No. 3,165,133,dated- Sept. 24, 1963. Divided and thin application June 3, i963, Ser.No. 2%,138

s Claims. (ill. 219-469) ,This application is a division of applicationSerial No. 30,971, filed May 23,1960, now Patent No. 3,105,133, datedSeptember 24, 1963.

This invention relates to an improved heat transfer roll and rotaryconductors therefor such as are used for transmitting electrical signalsindicating temperature of the roll.

More particularly the invention contemplates use in an electricallyheated hollow heat transfer roll having a cylindrical outer surface. Theroll is rotatably mounted on a shaft and aheater such as electricalresistance elements are positioned within the roll supplied byelectrical conductors which are controlled by a temperature sensitiveswitch. The invention contemplates the provision of the roll withimproved means for preventing the danger of confiagration or explosionin the event of an atmosphere of explosive gas being present such as maybe caused by contact of the heated roll with materials which volatilizewith heat. The invention further contemplates an improved means forelectrically measuring the temperature of the roll so as to effectivelyand accurately control the roll heater with the measuring meanstransmitting electrical signals which are a function of the temperatureof the roll through an improved rotary conductor.

In measuring the temperature of the outer surface of the roll anelectrical measuring device such as a thermocouple is well suited forcontinually reading the roll temperature. The electrical signal obtainedfrom the thermocouple is fed through a rotary connection or conductor toan electrical control which is usually stationary at the end of the rolland operates to regulate the operation of the heaters for the roll. Withthis type of control it has heretofore been difficult to obtain veryclose temperature control of the roll surface since the voltage outputsof the thermocouple are very small and losses will occur in the rotaryconnector causing an incorrect signal to be received. These losses aredimcult to control since any resistance such as which normally occurs ina slip ring type of arrangement will result in signal loss.

An object of the invention is to provide a heat transfer roll with animproved electrical heating arrangement and improved apparatus forcontrolling the application of heat and for safely effecting thetransfer of heat; and to provide a roll in which the danger ofexplosions or con flagration is greatly reduced.

An object is to provide an improved means for measuring the temperatureof a rotating roll and for producing an accurate electrical signalcorresponding to temperature. A further object of the invention is toprovide an improved rotary oonductor capable of conducting very lowvoltages without fluctuation due to relative rotation between touchingelectrical conductive members.

A further object of the invention is to provide an improved rotaryconductor which has substantially zero resistance so that there is novoltage drop through the conductor, and so that the conductor is capableof conducting the very small electrical signals generated by athermocouple on a rotating roll and transmitting them to a stationarymember which varies the liow of elecments in the specification, claims,and drawings, in which:

FIGURE 1 is .a sectional view taken through a form of heat transferroll; and

FIGURE 2 is a fragmentary sectional view taken substantially along IIIlof FIGURE 1.

In the arrangement of FIGURES 1 and 2, a rotor assembly 3t) is providedhaving a cylindrically shaped shell 31 which is provided with radialendwalls 32 and 33. The shell is mounted by means of bearings 34 and 35on a hollow coaxial stationary shaft 36.

Stationarily mounted on the shaft 36 and positioned within the shell 31in heat transfer relationship thereto are axially extending tubularheating elements 37. The elements are mounted on spiders 38 and 39 whichare secured to the shaft 36. Supported between the spiders is an annularreflector 4d for reflecting the heat outwardly toward the shell.Electrical wires 41 are connected to the endsof the heating elements 37and the wires are led through openings 42 and 43 in the shaft to passdown the center of the hollow shaft 36.

The electrical circuit to the heating elements 37 is controlled by afirst thermal responsive element 44 and asecond thermal responsiveelement 4-5. The first element 44 is mounted to be responsive to thetemperature of a shell at a first location, preferably substantially atthe axial center of the shell. The second thermal responsive element 45is axially displaced from the first element and is preferably at the endof the shell. The thermal element 45 has a probe end which projects intoan outwardly drilled hole 46 in the shell and the thermal element 44 hasa similar probe which projects int-o a drilled hole 47 in the shell. Theelements are held in place such as by screws with a screw 48 threadedinto the shell to hold the element 45 in place, and a screw 49 threadedinto the shell to hold the element 44 in place.

The thermal responsive elements generate an electrical voltagecorresponding to the temperature of the shell and are connected so thattheir output is an average ofthe outputs of the two elements 44 and 45.In other words, the elements are connected in multiple so that anaverage temperature response is received and a temperature between thatof the center and of the cooler ends of the shell is provided for acontrol signal. For this purpose, the electrical wires 59 and 51 arerespectively connected to the elements 44 and 45 and each set of leadsare connected to two brushes 52 and 53.

The thermal sensitive elements are preferably of the thermocouple typewhich generate a very small electrical output in the millivolt range.The output circuit must have substantially no resistivity to it whichwould cause a drop in millivolts and throw off the temperatureindication; however, a connector must be provided which will acco-mmodate rotation of the shell.

The brushes '52 and 53 are in the form of an elongated wire or ribbon.The wire brushes are connected to supporting posts 54 and 55 at one end,and supporting posts 56 and 57 at the other end connect to tensionsprings "58 and 59 which hold the elongated brushes 52 and 53 againstslip rings as and 61. The slip rings 60 and 61 are onepiece annularmetal rings with a slight indentation in the outer surface to receivethe wire brushes 52 and'53, and the slip rings are mounted on aninsulating support 62, shown in the form of fiat discs held together tosupport the rings. In other Words, an electrical connector is providedincluding wire brush elements 52 and 53 and slip ring elements so and 61with said elements being relatively rotatable and the brush elements 52and 53 shown as rings. The support posts 54- and 5d, and S6 and 57 atthe ends of the wire brushes are of insulative material.

The wire leads 63 and 64 from the thermal elements will connect to aswitch means for controlling the electrical supply to the leads 41 forthe heating elements, similar to the connections shown in thearrangement of FIGURE 2.

As will be appreciated by those versed in the art the wire leads 63 and64 may connect the various types of controls for regulating varioustypes of heaters for the roll. It is import-ant that an accuratemillivolt signal be obtained which is truly representative of thetemperature signal received from the roll which does not fluctuate indifferent rotational positions of the roll as it is rotated and whichdoes not fluctuate with age or operating life of the mechanism. Thesurfaces between the wires or ribbons and the slip ring surfaces againstwhich they engage a're self-cleaning and with rotation will prevent theaccumulation of any surface films or corrosive layers which wouldprovide an electrical resistance at the point of engagement between thewire and the slip ring surfaces.

The rotating slip rings are preferably formed of a material such asbronze which is highly conductive, and which readily remains clean withthe rotation of the wires. A strong steel Wire such as piano wire isWell suited for use for the ribbons.

, Thus, it will be seen that I have provided an improved and simplifiedrotary electrical connector which meets the objectives and advantagesabove set forth. The mechanism is non-complicated for purposes ofmanufacture and avoids disadvantages in structures heretofore available,providing a rotary connector or conductor which is capable of handlingmillivolt signals without offering resistance to the flow of electricityand which transmits an accurate electrical signal with continued use.

The positive electrical connection between the relatively movingpartsand the lack of resistance therebetween prevents any inadvertentsparking and also contributes to the safety and explosion-proof featuresof the structure.

The inside of the shell, as illustrated for example in FIGURE 1, ispressurized with a low pressure on the order of three pounds per squareinch, with a non-combustible gas. As shown, one end of the shaft 36 isclosed with a threaded plug Mia, and a pressure supply line from a pump66 is connected to the other end of the shaft to deliver a gas such asair. The air pressurizes the inside of the shell through the openings 42and 43 and the bearings 34 and are such that very little of the pressureis permitted to escape. The leakage of non-combustible gas through theopenings which are present prevents any outside gases from entering theshell.

The rotors may be provided with means for driving them in rotation forcontact with the surface area that is to be heated or they may be usedas an idler with the surface being heated rotating the rotor throughfriction. Thesestructures may be employed for various heating purposesand can be used for softening thermoplastic materials to sealcontainers. It is also contemplated to place an embossed outer sleeveover the shell for engagement with material to etch an embossed designin it, for one use of the rotors.

Thus it will be seen that I have provided an improved and simplifiedelectrically heated heat transfer roll which meets the objectives andadvantages above set forth. The mechanism avoids disadvantages instructures heretofore available and is reliable and effective inoperation.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

' shaped shell, an electrically energized heating element 4- I claim asmy invention: 1. A heat transfer roll comprising a cylindricallystationarily mounted within the shell, a'therrnal sensitive elementmounted for rotation with the shell and generating an electrical voltagecorresponding to the temperature of the shell, a control switch meansfor controlling the electrical supply to said heating element, and aconnector between said thermal element and said control switch meansincluding slip ring members and relatively rotating elongated wire brushmembers supported at their ends with an intermediate portion intensioned positive rubbing contact with said ring members and said ringand brush members being relatively rotatable so that a substantiallynegligible electrical resistance is otfered by said connector and anaccurate voltage will be received by the control switch means from saidthermal element.

2. A heat transfer roll comprising a cylindrically shaped shell, anelectrically energized heating element stationarily mounted within theshell, a thermal sensitive element mounted for rotation with the shelland generating an electrical voltage corresponding to the temperature ofthe shell, a control switch means for controlling the electrical supplyto said heating element, and a connector between said thermal sensitiveelement and said control switch means including slip ring memberselectrically insulated from each other and connected to said thermalsensitive element and including a pair of wire brush members.

anchored at one end and provided with biasing means urging the brushmembers into sliding contact with the outer face of said ring members,said brush members and ring members being relatively rotatable, saidbrush mem-. bers connected to said switch means and providing with theslip ring members a substantially negligible resistance so that anaccurate voltage will be received by the control switch means from saidthermal element.

3. A heat transfer roll comprising a cylindrically shaped shell, anelectrically energized heating element stationarily mounted within theshell, a thermal sensitive element mounted for rotation with the shelland generating an electrical voltage corresponding to the temperature ofthe shell, a control switch means for controlling the electrical supplyto said heating element, a connector between said thermal sensitiveelement and said control switch means structurally accommodatingrotation of the shell, means for pressurizing the inside of said shelldelivering a non,- cornbustible gas under pressure thereto so that entryof outside gases into the shell and contact with the heating element ispositively prevented and means closing the shell preventing the freeescape of gas from within the shell, the shell interior being under apositive pressure so that said outside gases will not enter the shell.

4. A heat transfer roll comprising a cylindrically shaped shell, astationary hollow support shaft for the shell, hearings on said shellfor rotatably supporting said shell, an electrically energized heatingelement stationarily mounted on said shaft within the shell, a thermalsensitive element mounted for rotation with the shell and generating anelectrical voltage corresponding to the temperature of the shell, acontrol switch means for controlling the electrical supply to saidheating element, a connector between said thermal sensitive element andsaid control switch means structurally accommodating rotation of theshell, means defining openings through the hollow support shaft withinthe shell, a pressure supply connection on said shaft for directing asupply of non-combustible gas into said shaft and said shell so thatentry of outside gases and contact with the heating element ispositively prevented and means preventing the free escape of gas fromsaid shaft and shell, the interior of said shell being under a positivepressure so that ambient air will not enter the shell.

5. A heat transfer roll comprising, a heater for heating said shell, anelectrically energized control for controllably operating the heater, athermal sensitive element mounted for rotation with the shell andgenerating an electrical voltage corresponding to the temperature of theshell, a control switch means for controlling the electrical supply tosaid control, and a connector between said thermal element and saidcontrol switch means including slip rings and relatively rotatingelongated Wire brushes supported at their ends with an intermediateportion in rubbing tensioned positive rubbing contact with said rings sothat a substantially negligible electrical resistance is offered by theconnector and an accurate voltage will be received by the control switchmeans from said thermal element.

6. A heat transfer roll comprising a cylindrically shaped shell, astationary hollow support shaft for the shell, bearings on said shellfor rotatably supporting said shell, an electrically energized heatingelement stationarily mounted on said shaft within the shell, a thermalsensitive element mounted for rotation with the shell and generating anelectrical voltage corresponding to the temperature of the shell, acontrol switch means for controlling the electrical supply to saidheating element, a connector between said thermal sensitive element andsaid control switch means structurally accommodating rotation of theshell, said connector including slip rings and elongated wire brushes inrubbing contact with said rings and being rotatable relative to therings extending substantially tangential to the rings and provided withbiasing means urging the wires into sliding contact with the face of therings so that negligible resistance is afforded and a spark-proofengagement is provided avoiding the danger of explosion, means definingopenings through the hollow support Within the shell, and a pressuresupply connection on said shaft for directing a supply ofnon-combustible gas into said shaft and said shell so that entry ofoutside gases and contact with the heating element is positivelyprevented to avoid danger of explosion.

References Cited in the file of this patent UNITED STATES PATENTS1,978,081 Hanson Oct. 23, 1934 2,047,372 Jalens July 14, 1936 2,504,440Miess Apr. 19, 1950 2,571,426 Doniak Oct. 16, 1951 2,881,297 FriedmanApr. 7, 1959 2,919,556 Hold Nov. 10, 1959 FOREIGN PATENTS 309,291 G e tri a n P 2?

1. A HEAT TRANSFER ROLL COMPRISING A CYLINDRICALLY SHAPE SHELL, ANELECTRICALLY ENERGIZED HEATING ELEMENT STATIONARILY MOUNTED WITHIN THESHELL, A THERMAL SENSITIVE ELEMENT MOUNTED FOR ROTATION WITH THE SHELLAND GENERATING AN ELECTRICAL VOLTAGE CORRESPONDING TO THE TEMPERATURE OFTHE SHELL, A CONTROL SWITCH MEANS FOR CONTROLLING THE ELECTRICAL SUPPLYTO SAID HEATING ELEMENT, AND A CONNECTOR BETWEEN SAID THERMAL ELEMENTAND SAID CONTROL SWITCH MEANS INCLUDING SLIP RING MEMBERS AND RELATIVELYROTATING ELONGATED WIRE BRUSH MEMBERS SUPPORTED AT THEIR ENDS WITH ANINTERMEDIATE PORTION IN TENSIONED POSITIVE RUBBING CONTACT WITH SAIDRING MEMBERS AND SAID RING AND BRUSH MEMBERS BEING RELATIVELY ROTATABLESO THAT A SUBSTANTIALLY NEGLIGIBLE ELECTRICAL RESISTANCE IS OFFERED BYSAID CONNECTOR AND AN ACCURATE VOLTAGE WILL BE RECEIVED BY THE CONTROLSWITCH MEANS FROM SAID THERMAL ELEMENT.